Group 7 Flashcards

All 18 cards in this deck

What are the colour and physical state of chlorine at room temperature?

Pale green gas.

What are the colour and physical state of bromine at room temperature?

Red-brown liquid.

What are the colour and physical state of iodine at room temperature?

Dark grey solid.

What happens to melting point, boiling point and density going down Group 7?

They increase down the group.
e.g. chlorine is a gas, bromine a liquid and iodine a solid at room temperature.

Predict the colour and physical state of astatine at room temperature.

Grey/black solid.

What is the chemical test for chlorine gas, and the result?

Hold damp blue litmus paper in the gas: it first turns red, then is bleached white.

What type of compound is formed when a halogen reacts with a metal?
e.g. burning sodium lowered into a gas jar of chlorine

A metal halide — sodium chloride (NaCl), seen as white crystals.

What is the balanced equation for the reaction between aluminium and chlorine?

$2Al + 3Cl_2 \rightarrow 2AlCl_3$

What is formed when a hydrogen halide dissolves in water?

An acidic solution.
e.g. hydrogen chloride dissolves to form hydrochloric acid.

What is seen when chlorine water is added to colourless potassium bromide solution and shaken?

The mixture turns yellow/orange/brown, because bromine is displaced.

Write the half equation for the formation of bromine from bromide ions.

$2Br^- \rightarrow Br_2 + 2e^-$

Write the half equation for the reduction of chlorine molecules to chloride ions.

$Cl_2 + 2e^- \rightarrow 2Cl^-$

In a halogen displacement reaction, which species is oxidised and which is reduced?

The halide ions lose electrons, so are oxidised; the halogen molecules gain electrons, so are reduced.

What is the order of reactivity of chlorine, bromine and iodine?

Chlorine > bromine > iodine — reactivity decreases down Group 7.

Give two reasons why an electron is gained less easily further down Group 7.

The outer shell is further from the nucleus and there is greater shielding (more shells), so there is less nuclear attraction for the extra electron.

How do displacement reactions show the order of reactivity of chlorine, bromine and iodine?

A more reactive halogen displaces a less reactive one from its halide solution (seen as a colour change). Chlorine displaces bromide and iodide; bromine displaces only iodide; so chlorine > bromine > iodine.

True or false? Astatine would displace iodine from sodium iodide solution.

False. Astatine is below iodine in Group 7, so it is less reactive and cannot displace iodine.

What is seen when chlorine water is added to colourless sodium iodide solution, and why?

The solution turns brown, because chlorine displaces iodine from the iodide.